Actuator systems for shifting a control device that is pressure-loaded against the shift direction may incorporate an actuator element housed in a system enclosure that is axially movable at least in the shift direction by an internal advance mechanism.
An actuator system of this type has been known in prior art, serving to actuate control devices such as valves, pressure regulators and the like but most particularly for use in submarine oil and gas exploration and production equipment. The actuator system can be employed equally well in comparable land-based, difficult-to-access or remote equipment.
When the switching device is shifted against the direction of the pressure load, the actuator element is moved axially so that in its extended forward position it serves to shift the control device into the operational ready-state. When the actuator element is homed, i.e., moved back and away from the shift direction, the control device is deactivated. An actuator system of this type is provided with a suitable enclosure protecting it from the elements in a marine or land-based environment. With current actuator systems, however, it is not possible in an emergency to manually operate the system by simple external intervention.